Gas turbine engine with improved afterburner

ABSTRACT

The disclosure shows an afterburner for a gas turbine engine comprising fuel injectors and concentric, annular, V-shaped gutters which function as flameholders. Links are pivotally mounted at their opposite ends to the gutters and to beams. The beams are pivoted on the outer casing of the afterburner and align the pivot axes of the links and the bisectors of the gutters with the direction of hot gas flow toward the gutters in the &#39;&#39;&#39;&#39;hot&#39;&#39;&#39;&#39; condition of the afterburner to prevent twisting of the gutters when their material strength is weakest.

United States Patent Arand [54] GAS TURBINE ENGINE WITH IMPROVEDAFTERBURNER [72] Inventor: John K. Arand, Palos Verdes Peninsula,

Calif.

[73] Assignee: General Electric Company [22] Filed: May 25, 1970 [21]Appl. No.: 40,298

[52] 1.1.8. CL ..60/26l, 60/3931, 60/3972 [51] Int. Cl ..F02l( 3/08 [58]Field of Search ..60/26l, 39.72, 39.31

[56] References Cited UNITED STATES PATENTS 2,714,287 8/1955 Carr..60/261 3,056,261 10/ 1962 Krabacher.. .....60/261 3,102,392 9/1963Bauger ..60/39.72

1 Mar. 7, 1972 FOREIGN PATENTS OR APPLICATIONS 821,286 10/1959GreatBritain ..60/39.72 944,202 12/1963 Great Britain ..60/39.72

Primary Examiner-Douglas Hart Attorney-Derek P. Lawrence, Edward S.Roman, Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Fonnan [5 7]ABSTRACT The disclosure shows an afterbumer for a gas turbine enginecomprising fuel injectors and concentric, annular, V-shaped gutterswhich function as flameholders. Links are pivotally mounted at theiropposite ends to the gutters and to beams. The beams are pivoted on theouter casing of the afterburner and align the pivot axes of the linksand the bisectors of the gutters with the direction of hot gas flowtoward the gutters in the hot condition of the afterbumer to preventtwisting of the gutters when their material strength is weakest.

4 Claims, 5 Drawing Figures PATENTEDHAR 7 I972 SHEET 1 [IF 3 INVENTOR.JOHN K. ARAND PATENTEBHAR 7 I972 3. 646. 763

SHEET 2 [IF 3 INVENTOR. JOHN KAR ND PATENTEDMAR I 1972 3,646,763

SHEET 3 BF 3 INVENTOR. JOHN K. ARAND' GAS TURBINE ENGINE WllTI-IIMPROVED AFTERBURNER The invention described and claimed in the U.S.patent application herein resulted from work done under U.S. Governmentcontract FA-SS-66-6. The U.S. Government has an irrevocable,nonexclusive license under said application to practice and havepracticed the invention claimed herein, including the unlimited right tosublicense others to practice and have practiced the claimed inventionfor any purpose whatsoever.

The present invention relates to improvements in gas turbine engineshaving afterbumers for augmenting the energy level of a hot gas streamto be discharged from a propulsion nozzle.

In such afterburners fuel is injected into a hot gas stream to augmentits energy level. Flameholders are mounted immediately downstream of theinjectors to establish a stable framefront or localized combustion zonefor the augmenting fuel.

V-shaped sheet metal gutters have been found to be quite effective asflameholders. Such flameholders must operate in an area of extremelyhigh temperature at which the strength of the gutter material is quitelow. Because of the relatively thin metal sections required by weightlimitations and for other reasons, flameholder gutters have been subjectto bending and twisting loads which result in distortion of the guttersin relatively short periods of operation.

It has been proposed to duct cooling air to flameholder gutters toreduce their metal temperatures and thus increase their strength. Thisapproach requires bleeding of pressurized air from the engine whichreduces overall engine efficiency. It also involves complexity in themanufacture of the flameholder system.

Accordingly, the primary object of the invention is to prevent bending,twisting and other deformation of flameholder gutters in a simple,effective manner to thereby significantly increase their service life.

These ends are attained by a mounting system which, when the afterburneris in operation in its hot condition, aligns the bisector of theV-shaped gutter and the pivot axes of mounting links with the directionof flow of the hot gas stream toward the gutter. Preferably, the linksare mounted on beams which are pivoted on the casing of the afterburnersection of the engine and have pivoted links connecting their inner endsto a central casing or plug.

The above and other related objects and features of the invention willbe apparent from a reading of the following description of thedisclosure found in the accompanying drawings and the novelty thereofpointed out in the appended claims.

In the drawings:

FIG. 1 is a schematic showing of a gas turbine engine incorporating anafterburner for supersonic propulsion;

FIG. 2 is a partial longitudinal section showing the afterburner ingreater detail in its hot position;

FIG. 3 is a section taken on line IIlIIl in FIG. 2;

F IG. 4 is a section taken on line IVIV in FIG. 2; and

FIG. 5 is a section similar to FIG. 2 showing the afterburnerflameholder in a cold position.

FIG. 1 schematically illustrates a gas turbine engine of the typeemployed for supersonic flight. Air enters an inlet comprising a spikeI0 and is then compressed in an axial flow compress'or 12. Thiscompressed air supports combustion of fuel in a combustor 14 to generatea hot gas stream. The hot gas stream drives a turbine 16 which in turn,through a shaft 18, powers the rotor of the compressor 12. The energylevel of the hot gas stream is then augmented by the combustion offurther fuel in an afterburner or augmenter 20. The augmented gas streamis then discharged from a variable area, convergentdivergent nozzle 22to provide the necessary thrust for supersonic flight.

In subsonic flight operation the hot gas stream may or may not beaugmented in the afterburner and the nozzle may be adjusted to otherthan the illustrated convergent-divergent configuration.

Referencing FIGS. 1 and 2 it will be noted that the hot gas stream hasan annular flowpath as it enters the afterburner. This flowpath isdefined by an engine casing 24 and a central plug 26 which is supportedon appropriate frame structure (not shown).

The afterburner includes fuel injectors 30 (see also FIG. 4) andflameholders in the form of annular V-shaped gutters 32. The injectorsmay comprise tube bundles which are mounted in angularly spaced relationon the casing 24. Openings in the tubes spray fuel into the hot gasstream and a stabilized flamefront or combustion zone is maintained bythe gutters 32. This type of an afterburner combustion mechanism isknown per se.

The gutters 32 are preferably in the form of sheet metal fabricationshaving mounting lug openings 36 in their troughs or apices (FIG. 3).Mounting lugs 38 extend through the openings 36 and have wings 40 curvedto match the troughs of the gutters. These wings are secured to thegutters, as by brazing. Links 42 are connected on opposite sides of eachlug 38 by pins 44. The opposite ends of each pair of links 42 areconnected by pins 46 to beams 48 angularly spaced around the casing 24.As can be seen from FIG. 4, there is a linkage con nection between eachbeam and each gutter.

Each of the beams 48 is pivotally mounted, at its outer end, on thecasing 24 by a pin 50 and a lug 52 secured to the casing. A link 54 isconnected to each beam 48, adjacent its inner end, by a pin 56. Eachlink 54 is angled in an upstream direction toward the plug 26 and ispivotally connected thereto by a pin 58 extending through a lug 60.

The gutters 32 operate in an extremely hot environment resulting ingreatly reduced load carrying capacity of the gutter material ascompared with more normal lower temperature environments. The describedmounting system is particularly adapted to minimize stresses on thegutters when the hot gas stream is at a maximum temperature and metalstrength is at a minimum.

It will first be noted that relative radial and axial differentialdimensional growth can and does occur between the casing 24 and the plug26. The beams 48 and the links 56 readily accommodate such growth andyet positively position the upstream ends of the links 42 in their hot"position of minimum material strength, all without imposing any stresson the gutters which would tend to distort them in a twisting fashion.The links 42 allow differential growth of the gutters 32 relative to thebeam system independently of each other, again without imposing anyconstraining twisting stress on the gutters in their hot position.

The gutters and the overall support system therefor are dimensioned (ascould be done by a person skilled in the art) so that at the hottestnormal operating condition the bisector of the gutter angle, line x inFIG. 2, is aligned with the axes of the associated linkage pins 44 and46 and also aligned with the direction of hot gas stream flow toward thegutter. This means that there are no twisting forces on the gutters andthe stresses thereon are reduced to the simple, minimum level imposed bythe hot gas stream in the direction of flow.

FIG. 5 illustrates a cold" position of the gutter mounting assemblywithin the hot position shown by broken lines for comparison. From thisFigure it will be seen that when the described alignment of the bisectorx is not maintained there is a moment arm either about the gutterrelative to the axis of pin 46, or both. In any case a twisting of thegutter occurs which imposes higher stresses on the gutter beyond theminimum stress condition, described in connection with FIG. 2. However,higher stresses can be tolerated at such a cold" condition due to theincreased strength capabilities of the gutter material at reducedtemperatures, albeit such reduced temperatures may be in excess of l,200F.

Various modifications of the preferred embodiment, herein described,will appear to those skilled in the art within the spirit and scope ofthe present inventive concepts which are to be derived solely from thefollowing claims.

Having thus described the invention what is claimed as novel and desiredto be secured by Letters Patent of the United States is:

l. A gas turbine engine comprising: means for generating a hot gasstream, a propulsive nozzle from which the hot gas stream is discharged,and

an afterbumer for increasing the energy level of the hot gas streamimmediately prior to its discharge from the propulsive nozzle, saidafterbumer comprising,

an outer casing,

fuel injectors within said casing,

flameholder means in the form of a plurality of concentric,

annular, V-shaped gutters, each having its apex in an upstream directiontoward said fuel injectors, each gutter having a bisector which extendsfrom its apex intermediate its sides,

links pivotally connected at their downstream ends to the apexes of thegutters and spaced circumferentially therearound, the pivotal axes ofsaid links respectively lying on the bisectors of the gutters,

mounting means pivotally connected to the upstream ends of the links andrespectively aligning the pivot axes of the links and the bisector ofeach gutter with the direction of hot gas flow theretoward in the "hot"condition of the afterbumer,

thereby eliminating any tendency to twist the gutters when theirmaterial strength is weakest.

2. A gas turbine engine as in claim 1 wherein,

the mounting means comprise a plurality of beams pivotally mounted onsaid outer casing and angularly spaced therearound.

3. A gas turbine engine as in claim 2 wherein,

the afterbumer additionally includes an inner plug and the mountingmeans further includes links respectively angled from the inner endportions of said beams upstream toward said plug,

said beam links being pivotally connected at their opposite endsrespectively to said beans and to said plug.

4. A gas turbine engine as in claim 2 wherein,

lugs are secured to the gutters, extend in an upstream direction and arealigned with the bisectors of said gutters and the downstream ends ofthe links are pivotally connected to said lugs,

1. A gas turbine engine comprising: means for generating a hot gasstream, a propulsive nozzle from which the hot gas stream is discharged,and an afterburner for increasing the energy level of the hot gas streamimmediately prior to its discharge from the propulsive nozzle, saidafterburner comprising, an outer casing, fuel injectors within saidcasing, flameholder means in the form of a plurality of concentric,annular, V-shaped gutters, each having its apex in an upstream directiontoward said fuel injectors, each gutter having a bisector which extendsfrom its apex intermediate its sides, links pivotally connected at theirdownstream ends to the apexes of the gutters and spacedcircumferentially therearound, the pivotal axes of said linksrespectively lying on the bisectors of the gutters, mounting meanspivotally connected to the upstream ends of the links and respectivelyaligning the pivot axes of the links and the bisector of each gutterwith the direction of hot gas flow theretoward in the ''''hot''''condition of the afterburner, thereby eliminating any tendency to twistthe gutters when their material strength is weakest.
 2. A gas turbineengine as in claim 1 wherein, the mounting means comprise a plurality ofbeams pivotally mounted on said outer casing and angularly spacedtherearound.
 3. A gas turbine engine as in claim 2 wherein, theafterburner additionally includes an inner plug and the mounting meansfurther includes links respectively angled from the inner end portionsof said beams upstream toward said plug, said beam links being pivotallyconnected at their opposite ends respectively to said beans and to saidplug.
 4. A gas turbine engine as in claim 2 wherein, lugs are secured tothe gutters, extend in an upstream direction and are aligned with thebisectors of said gutters and the downstream ends of the links arepivotally connected to said lugs.